The present invention relates to a digital information recording medium having a limited storage amount and premised on variable bit rate recording.
The present invention also relates to a digital information recording/playback system using a digital information recording medium having a limited storage amount.
Furthermore, the present invention relates to a digital video recorder for recording and playing back information such as digital moving pictures and the like, which are compressed by MPEG.
In recent years, systems for playing back the contents of optical discs that record video data (moving pictures), audio data, and the like have been developed, and have prevailed for the purpose of playing back movie software titles, karaoke data, and the like as in LDs (laser discs), video CDs (video compact discs), and the like.
DVD (digital versatile disc) standards that use MPEG2 (moving picture expert group) international standards, and also use an audio compression scheme such as AC-3 (digital audio compression), or the like, have been proposed. The DVD standards include read-only DVD video (or DVD-ROM), write-once DVD-R, recordable/readable DVD-RW (or DVD-RAM).
The DVD video (DVD-ROM) standards support MPEG2 as a moving picture compression scheme, and AC-3 audio and MPEG audio in addition to linear PCM as audio recording schemes in accordance with the MPEG2 system layer. Furthermore, the DVD video standards are configured by adding sub-picture data obtained by runlength-compressing bitmap data for superimposed dialogs, and presentation control data (navigation data) for fastforward, rewind, data search, and the like. The standards also support the UDF Bridge format (a hybrid of UDF and ISO9660) to allow computers to read data.
An optical disc currently used in DVD video (DVD-ROM) is a single-sided, single-layered 12-cm disc having a storage amount around 4.7 GB (gigabytes). A single-sided, two-layered disc has a storage amount around 9.5 GB, and a double-sided, two-layered disc is capable of recording a large amount of data around 18 GB (when a laser of a wavelength of 650 nm is used for reading).
An optical disc currently used in DVD-RW (DVD-RAM) is a 12-cm disc, and has a storage amount of 2.6 GB (gigabytes) on one surface, i.e., 5.2 GB on the two surfaces. The currently available DVD-RAM optical disc has a smaller storage amount than that of a DVD-ROM disc of the corresponding size. However, technical developments for expanding the amount of the DVD-RAM disc have been extensively made, and it is certain that a DVD-RAM disc having a storage amount more than 4.7 GB on one surface will be available in the near future.
However, since an MPEG2 video file that can obtain high picture quality has a large data size, the currently available DVD-RAM disc (single-sided 2.6 GB disc or double-sided 5.2 GB disc) does not always have a sufficient recordable time (around 1 hour for 2.6 GB disc, around 2 hours for 5.2 GB disc).
That is, the storage amounts of individual DVD-RAM discs do not have an enough margin for the purpose of long-time moving picture recording in the status quo, and efficient data management (release of unnecessary storage areas, management of variable recording rates in correspondence with the remaining recordable amount and/or monitoring of the remaining recordable time at a variable recording rate, and the like) is required. Even if the storage amount of a DVD-RAM disc increases in the future, requirements for longer-time recording arise accordingly, and efficient data management is also required.
In an optical disc such as a DVD-RAM on which data can be written or rewritten, a function of allowing the user to easily edit data is demanded. However, no recording/playback apparatus which can be easily handled by the user for home use is available to date.